Heretofore, when it was desired to obtain increased air flow through a carburetor induction passage having a fixed venturi therein, such was accomplished by enlarging the throat of the venturi until a workable compromise was attained as between the available metering force at a known low air flow and the high air flow horsepower requirements as of a particular engine. When such a compromise was attained, any desired additional air flow capacity had to be supplied as by adding secondary induction passage means or systems which were, in the main, a duplication of the primary induction passages. Such secondary induction passage means, in turn, required that the associated intake manifold of the engine also be provided with additional inlet apertures into which the secondary induction passages would discharge. This, of course, meant that a particular engine could not accommodate a single stage carburetor and a multi-stage multi-induction-passage carburetor without also having to have differing intake manifolds which would "match-up" with such different types of carburetors.
The invention as herein disclosed and claimed is primarily directed to the solution of the problems of the prior art and to provide a carburetor structure which can provide desired additional air flow capacity without the need for providing additional induction passage means respectively discharging directly into the engine intake manifold.